Conical Trash Rack Cleaning With Underwater Debris Discharge
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Solution Overview
Problem
Existing hydroelectric power plant screen arrangements face challenges in effectively cleaning debris, particularly thin particles like leaves and paper, which adhere to the screen bars and are unsatisfactorily removed by existing scrapers or water flow, and require complex mechanisms like float-actuated discharge pipes.
Innovation Solution
A conical rake arrangement with a scraper that tapers into a downpipe, discharging screenings underwater, and a scraper mechanism that rotates around the cone axis to collect and convey debris to the downpipe, assisted by a vortex flow for efficient discharge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a screen arrangement with scrapers is used to clean debris from the shaft crown, then the screen can be cleaned, but thin particles like leaves and paper adhere to the screen bars and are not effectively removed
Solution Approach 1:
The invention uses a water jet system to remove thin particles from the screen bars. High-pressure water jets are directed against the screen bars to dislodge adhering particles such as leaves and paper, which mechanical scrapers cannot effectively remove. This hydraulic cleaning method complements the mechanical scraping action to achieve complete debris removal.
Solution Approach 2:
The cleaning system is divided into multiple components: rotating scrapers for general debris removal and fixed water jet nozzles for thin particle removal. This segmentation allows each component to specialize in removing specific types of debris, with scrapers handling larger particles and water jets handling thin adhering particles, thereby improving overall cleaning effectiveness.
2Extent of automation
If a float-actuated discharge pipe mechanism is used to discharge screenings, then the discharge can be automated, but the device complexity increases
Solution Approach 1:
The discharge system is designed to operate automatically based on the accumulation of screenings. When screenings reach a certain level in the collection chamber, they naturally block the discharge opening, causing water to rise and automatically flush the screenings out through the discharge pipe. This self-regulating mechanism eliminates the need for complex float-actuated control systems while achieving automated discharge.
Solution Approach 2:
The invention converts the harmful effect of screened debris blocking the discharge opening into a beneficial automatic flushing mechanism. The blockage caused by accumulated screenings triggers the water level to rise, which automatically activates the flush to clear the screenings, transforming a potential problem into an automated control mechanism.
3Ease of operation
If screenings are discharged through the turbine area, then the discharge path is straightforward, but debris accumulation in the turbine area occurs
Solution Approach 1:
The invention extracts the discharge path from the turbine area by routing it through a separate underwater discharge line. The collection chamber is positioned downstream of the turbine, and screenings are discharged through a dedicated pipe that opens in the tailrace away from the turbine intake, completely separating the discharge path from the turbine operating area to prevent debris accumulation.
Solution Approach 2:
The invention introduces an intermediate collection chamber as a mediator between the screen and the final discharge location. Screenings are first collected in this chamber, then transported through an underwater discharge line to the final discharge point in the tailrace. This intermediate structure allows screenings to be handled separately from the turbine flow path, preventing direct deposition in the turbine area.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Ensures effective cleaning and simple discharge of screenings into an underwater area, preventing debris accumulation and reducing operational complexity by bypassing the turbine.
Implementation Method 1
a scraper running between the downpipe and the outer edge of the conical rake, which is rotatable about the cone axis
Implementation Method 2
the resulting axial flow through the downpipe, which extends into the funnel area and leads to a vortex flow in the funnel area, which supports the loosening of the screenings from the screen lamellae and the conveyance of the screenings to the downpipe
Data Source
Figure 1
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AI summary
A trash rack arrangement for a hydroelectric power plant between the upstream and downstream water levels (1, 2) is described, comprising an upstream-fed intake shaft (6) located upstream of a turbine (3), the shaft crown (6) of which terminates below an upstream water level (5) and is covered by a trash rack (11), and a scraper (17) resting on the trash rack (11) and rotatable about an axis. To create advantageous racking conditions, it is proposed that the trash rack (11) forms a cone tapering in the direction of flow and opening into a downpipe (12), that the downpipe (12) connects to a shut-off discharge pipe (13) opening in the downstream area, and that the scraper (17) running between the downpipe (12) and the outer edge of the conical trash rack (11) is rotatable about the axis of the cone.